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Transcript of 100411_manufacturing_techniques_and_process_challenges_schwarting_ebel_dorsch.pdf
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Manufacturing Techniques and Process Challenges
with CG-47 Class Ship Aluminum Superstructure
Modernization and Repairs
Richard Schwarting, P.E. and Greg Ebel
BAE Systems Ship Repair
T. James Dorsch, P.E.
BAE Systems Land and Armaments
Approved for Public Release, Distribution Unlimited, BAE Systems Communications Department
Ship Design and Materials Technology Panel (OCT 2011)
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Modernization of CG-47 Class
Current program to make design changes to reduce fatigue cracking in several areas
Additional cracking due to Stress Corrosion has been identified Aluminum alloy has become sensitized to stress corrosion in some areas
Repair requirements for sensitized material More stringent welding and inspection procedures
Methodology for repair and modernization Crack repair
Plate replacement
Modular replacement
Manufacturing challenges Dimensional tolerances
Non-destructive testing
Base metal restoration
Future efforts
Superstructure Weather Deck Crack
Structural Ship Alteration
Approved for Public Release, Distribution Unlimited, BAE Systems Communications Department
Ship Design and Materials Technology Panel (OCT 2011)
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CG-47 Ticonderoga Class Aegis Cruiser
Hull number 47 through 73
Produced from 1978-1994 Expected service life 40 years
Approximately 364 officers and enlisted crew
567 feet long
Steel hull, superstructure is aluminum to reduce topside weight
Anti-Air, Anti-Submarine, Anti- Surface, and Strike warfare
AEGIS system is the SPY-1A radar, which automatically detects and tracks air contacts to beyond 200 miles
Theater Ballistic Missile Defense capability demonstrated
Vertical Launch system
5 inch guns
Most powerful surface combatants in service with any Navy
Approved for Public Release, Distribution Unlimited, BAE Systems Communications Department
Ship Design and Materials Technology Panel (OCT 2011)
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Fatigue Cracking
Understood phenomenon with metals cyclic stress application, of sufficient stress magnitude and number of cycles will result in fatigue
cracking
This is particularly prevalent with aluminum which does not have a defined fatigue limit.
Further complications with fatigue Stress concentrations due to design
Stress concentrations due to weld bead geometry
Welding process induced residual stresses
Fatigue occurs in two steps Crack initiation
Crack propagation
Not surprising fatigue cracks
appear after some time duration
Approved for Public Release, Distribution Unlimited, BAE Systems Communications Department
Ship Design and Materials Technology Panel (OCT 2011)
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Superstructure Modernization
Planned or in-progress alterations Designing to meet modern sea service requirements
Assessing structural integrity after 17-25 years
Assessing building material degradation
Increasing ship capabilities and/or performance
Implement alterations during maintenance availabilities through the CG-47 class
Over 17 structural ship alterations planned or completed
Superstructure Designed Structural Ship Alterations CG 65: USS Chosin
Approved for Public Release, Distribution Unlimited, BAE Systems Communications Department
Ship Design and Materials Technology Panel (OCT 2011)
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New Cracks in Superstructures Observed
Unusual cracks, of significant length began to appear 5 years ago
Did not correlate with the usual stress concentrations
Navy investigations revealed cracks caused by Stress Corrosion Cracking
Superstructure weather deck
Internal structure plates in gas turbine intakes
Transverse bulkheads
All cracks located in 5456-H116 material CG-47 class ship superstructure primarily 5456-H116
Superstructure Weather Deck Crack
Internal Structure Gas Turbine Air Intake
Approved for Public Release, Distribution Unlimited, BAE Systems Communications Department
Ship Design and Materials Technology Panel (OCT 2011)
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Stress Corrosion Cracking
SCC requires 3 conditions: 1. Susceptible Material
Although 5XXX alloys are fairly immune to corrosion, microstructural
changes can impact corrosion
performance
2. Tensile loading
(sustained, not cyclic) Resulting from weld residual stress
3. Corrosive environment Sea water exposure is sufficient
5456-H116 materials were found to be sensitized 5456-H116 contains 4.5 to 5.7% magnesium (strengthening
alloy element)
Magnesium is very soluble in aluminum at high temperatures
At temperatures above 150F Mg2Al3 migrates and to grain boundaries creating a sensitized aluminum microstructure
susceptible to SCC
Exposure to elevated temperatures e.g., solar loading suspected
Rolling into plate process must be controlled to avoid sensitizing material
H116 temper for this purpose, stabilization
New requirement for H116 temper to test for intergranular corrosion (since 2004)
5456-H116 Normal Microstructure with Uniform
Distribution of the Magnesium Compounds, Mg2Al3 Sensitized 5456-H116 Microstructure with Mg2Al3
precipitation preferentially at the grain boundaries. Intergranular Stress Corrosion Cracking in 5456-H116
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Ship Design and Materials Technology Panel (OCT 2011)
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How to repair SCC cracks Identification of sensitized material
Take samples for ASTM G67 Intergranular corrosion test (destructive) Leaves holes in ship structure if test is negative
Weldability test run bead, examine for cracks
Degree of Sensitization Probe (non-destructive) Still under development (Navy funded project)
In situ metallography (non destructive) Need comparison standards
Range of Sensitization measured by Mass Loss Intergranular corrosion test 0 to 30 [mg/cm2] mass-loss, weld base material as-is
31 to 59 [mg/cm2] mass-loss, weld with base material
cold-working stress-relief (impact/peening)
60 and greater [mg/cm2] mass-loss, not weldable
Use low stress weld repair methods Low heat input pulse gas metal arc welding
Develop residual compressive stress by ultrasonic impact treatment before and after welding
Manual weld contour grinding
Use ASTM B928 certified repair materials (intergranular and exfoliation corrosion tested)
Approved for Public Release, Distribution Unlimited, BAE Systems Communications Department
Portable Metallography Kit
Ship Design and Materials Technology Panel (OCT 2011)
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Repair And Modernization Methodology
Localized Welding of Cracks - The extent of a crack region is identified by finding the crack-tip boundaries and mechanically
excavating the region, then weld repair with a full-penetration weld joint design.
Small to Large Insert Plate Removal of Cracked Base Material - If crack repairs are within regions of sensitized aluminum alloy base material then larger insert
plate removal to replace and renew the base material is required.
Approved for Public Release, Distribution Unlimited, BAE Systems Communications Department
Identified Crack Mechanically Excavate V-
Groove Joint
Full Penetration Weld
Identified Crack Remove Crack with a Plate
Cut-Out
Ship-Fit an Insert Renewal
Plate Weld Insert Plate, Full
Penetration
Ship Design and Materials Technology Panel (OCT 2011)
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Modular Modernization Structural Replacement Practical to replace large areas where multiple repairs or alterations are planned
Maximize shore side work to assure sections are fabricated under shop vs field conditions
Designed Structural Ship Alterations - Over 17 structural ship alterations planned or completed
- Aluminum alloy sensitization expands the work scope on some alterations due to ship specific conditions
Structural Repairs Lead to Aluminum Alloy Plate Renewal - Sensitized aluminum alloy would be removed if time and cost permits, opportunity to replace aluminum with new
material
Approved for Public Release, Distribution Unlimited, BAE Systems Communications Department
Structural Ship Alteration Designed to Strengthen a Deck to
Bulkhead Transition for a Gas Turbine Air Intake
Structural Ship Alteration Expanded for the Gas Turbine Air Intake on
Specific CG-47 Ships to Renew Adjacent Aluminum Alloy Plate
Ship Design and Materials Technology Panel (OCT 2011)
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Manufacturing Process Challenges
Degraded aluminum alloy base material
- Pits and surface corrosion traps contaminates which creates weld porosity
- Also cause false positive indications during dye penetrant testing - Increased porosity as found by radiographic inspection
Pulse Transfer, Gas-Metal-Arc-Welding [GMAW-P] - Welding Process Specification (WPS) and Procedure Qualification Report (PQR)
- Fabrication process step qualification based on environment influence
Assessing Base Material Influence on Qualified Welding Practices
- GMAW-P applications on new procured 5456-H116 aluminum alloy plate - GMAW-P applications on old marine service 5456-H116 aluminum alloy plate
Approved for Public Release, Distribution Unlimited, BAE Systems Communications Department
Radiograph of New Aluminum Alloy Base
Material [5456-H116] Utilizing WPS/PQR for
Semi-Automated GMAW-P
Radiograph of Sensitized Aluminum Alloy Base
Material [5456-H116] Utilizing WPS/PQR for
Semi-Automated GMAW-P WPS/PQR Fabrication Process Assessment for Porosity
Development with Overhead/Flat Welding Positions in Shop and
High Humidity Environments for Semi-Automated GMAW-P
Ship Design and Materials Technology Panel (OCT 2011)
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Enhanced Non-destructive Testing for Welds on Sensitized
Material
Sensitized or partially sensitized 5456-H116 base material Weld contour grinding, manual labor intensive process
Dye Penetrant Testing Technique on Sensitized Aluminum Alloy Required NDT process for 5456-H116 welded structures:
- Difficulty with interpretation and evaluation of relevant and non-relevant indications at stated acceptance limits
- Grinding surface of interest, weld reinforcement contouring, adds to instability with repeated PT inspections
Numerous non-relevant indications evaluation has been displayed on sensitized aluminum alloy
base material during dye penetrant testing.
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Approved for Public Release, Distribution Unlimited, BAE Systems Communications Department
Liquid Dye Penetrant Testing on Aluminum Alloy Weldment with
Sensitized Base Material and New Base Material. Required Weld Reinforcement Grinding on a PT Inspection
Surface for all CG-47 Class 5XXX Series Aluminum Weldments
Weld Solidification Ripples
Providing a Known Process
Variable for PT Interpretation
with Indication Relevancy
Ship Design and Materials Technology Panel (OCT 2011)
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Maintaining Ship Structural Dimensional Tolerances for
Modular Alterations
Approved for Public Release, Distribution Unlimited, BAE Systems Communications Department
Field Measurement with Portable Laser Tracker (Left) and Create
Best-Fit Models for Structural Ship-Fitting with Alterations (Right)
Structural Ship Building Tolerances with Two
Different Orientations of Measurement
Ship Superstructure Plate Deflection
Between Structural Members
Accommodation of Structural Tolerances for Structural Ship Alterations As designed
As built
After modifications during service
Actual dimensions after sea service deformation - Simply fabricating modules to meet the original design drawings, will not work. The boundaries of the modules
must meet design dimensions, BUT within weld joint fit-up tolerances to the remaining structure for alignment,
fairness, and bulkhead opposition as defined in new shipbuilding practices.
Measuring Existing Ship Superstructure - Portable three dimensional laser tracker to capture actual dimensions - Capture surface features and develop a computer model for best-fit repair alteration structural ship-fitting
Ship Design and Materials Technology Panel (OCT 2011)
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Conclusions
Challenges that have been encountered recently during the maintenance,
repair and modernization of CG-47 class cruiser superstructures.
- The most recent challenge is the discovery of sensitized aluminum alloy in areas of
the superstructure, and how that complicates modernization of these vessels.
Continual improvement in techniques and methods to overcome these challenges in a cost effective manner include:
- Detecting and testing sensitized aluminum (destructive and nondestructive techniques).
- Implementing specific weld profiles and surface finishes to aid NDT and reduce stress
concentrations.
- Applying cold work to develop surface compressive stresses to prevent stress corrosion cracking
(SCC).
- Performing enhanced non-destructive testing to better identify relevant indications.
- Using three dimensional coordinate measuring techniques to develop a model of the existing ship
structure so that accurate replacement modules can be fabricated prior to a docked ship
maintenance availability.
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Ship Design and Materials Technology Panel (OCT 2011)
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Future Work
Continuing Manufacturing Techniques and Improvements to Meet
Emergent Challenges
Application of non-destructive sensitization assessment techniques Portable electrochemical degree of sensitization probe. Comparative micrograph chart for degree of sensitization utilizing field metallography on aluminum alloy
5456-H116
Review the influences of automated welding on sensitized base material aluminum alloy Gas-metal-arc-welding, pulse transfer for single and multiple-pass fillet weldments
Evaluate single pass automated welding procedures on new and sensitized aluminum alloy per ASTM B928 for radiographic quantification of gas porosity
Quantify residual stress utilizing current welding and structural fabrication processes Focusing on practical implementations of laboratory trials utilizing experimental low-distortion-techniques are
applicable for deck-plate production.
Possibly Reduce grinding with the application of ultrasonic impact treatment / ultrasonic peening (UIT/UP) Mechanical property enhancement and fatigue improvement Achieve the final weld (toe) reinforcement contour and ultimately replace contour grinding.
Approved for Public Release, Distribution Unlimited, BAE Systems Communications Department
Ship Design and Materials Technology Panel (OCT 2011)
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ACKNOWLEDGMENTS The authors would like to thank and acknowledge the following organizations and teams for their technical
leadership with CG-47 class ship superstructure challenges, innovative contributions and content support of this
paper:
- Naval Sea Systems Command: SEA 05, SEA 21 - Naval Surface Warfare Center, Philadelphia
- CG-47 Superstructure Integrated Product Team - Naval Surface Warfare Center, Carderock
- Past Aluminum Task Force Findings - Alcoa Aluminum Corporation
- Regional Maintenance Centers: NSSA, SERMC, SWRMC, and PHNSY&IMF - BAE Systems Ship Repair - BAE Systems Land and Armaments: Combat Systems Division - BAE Systems Norfolk Ship Repair
REFERENCES (1) USS Chosin [CG-65] photo was released by the US Navy with the ID 020619-N-3228G-001
(2) ORourke, Ronald, Navy Force Structure and Shipbuilding Plans: Background and Issues for Congress, Congressional Research Service 7-5700, RL32665, December 23, 2010.
(3) H.W. Hayden, W.G. Moffatt, and J. Wulff, The Structure and Properties of Materials, Volume III, John Wiley & Sons, 1965.
(4) R.H. Leggatt, Residual Stresses in MIG Welded Aluminum Alloy Panels, The Welding Institute, MR340, 1987.
(5) Sielski, R. A, The History of Aluminum as a Deckhouse Material, Naval Engineers Journal, May 1987, pp 165-172
(6) BAE Systems Ship Repair maintenance availability historical stock photograph, COMNAVSEA release, 2010.
(7) Computer Model Rendering of CG47 Class Ship Superstructure from briefing, CG Superstructure Task Force Findings and Recommendation, NAVSEA21 release, 2011.
(8) BAE Systems Ship Repair maintenance availability historical stock photograph, COMNAVSEA release, 2010.
(9) BAE Systems Ship Repair maintenance availability historical stock photograph, COMNAVSEA release, 2010.
(10) Massachusetts Institute of Technology web course: http://ocw.mit.edu/courses/ materials-science-and-engineering/3-11-mechanics-of-materials-fall1999/modules /fatigue.pdf
(11) Aloca Aluminum Alloy Technical Reference Stock Microstructure Images for BAE Systems US Combat Systems.
(12) T.D. Burleigh, The Postulate Mechanisms for Stress Corrosion Cracking of Aluminum Alloys: A Review of the Literature 1980-1989, Corrosion, Volume 47 (No. 2), 1991, p 89-98.
(13) T.J. Summerson, Aluminum Association Task Group Exfoliation and Stress Corrosion Testing of Aluminum Alloys for Boat Stock, Proceeding of the 1974 Triservice Corrosion of Military Equipment Conference, 29-31 October 1974 Vol II, Seessions IV through VII.
(14) NAVSEA Technical Publication, Quality Assurance Requirements for Welding of 5XXX Series Aluminum Structures for CG-47 Class, March 2010.
(15) Empirical Data for Bar Graph: Alcoa Technical Center, Improved Gas Metal Arc Welding Procedures for Joining New to Old (Used) 0.25 Thick 5456-H116 Plates Developed Under Contract With BAE Systems Ship Repair, July 2009.
(16) Alcoa Technical Center, Improved Gas Metal Arc Welding Procedures for Joining New to Old (Used) 0.25 Thick 5456-H116 Plates Developed Under Contract With BAE Systems Ship Repair, July 2009.
(19) Department of Defense Manufacturing Process Standard, Fabrication, Welding, and Inspection of Ships Structure, MIL-STD 1689A, November 1990.
Approved for Public Release, Distribution Unlimited, BAE Systems Communications Department
Ship Design and Materials Technology Panel (OCT 2011)